The present invention generally relates to a rearview mirror assembly for a vehicle. More particularly, the present invention relates to a rearview mirror assembly having a turn indicator incorporated therein and/or a flexible circuit board. The invention also pertains to subassemblies for use in a rearview mirror assembly in which an LED is mounted to a circuit board in a novel manner.
Outside rearview mirror assemblies incorporating turn signal indicators have become increasingly popular. An example of one significant advantage that can be achieved by such a “signal mirror” is evident from FIG. 1, wherein vehicle A includes an outside signal mirror assembly 100. The driver of vehicle B is positioned in what is commonly referred to as the blindspot for the driver of vehicle A. Additionally, the driver of vehicle B is unlikely to see the rear turn signal lamp 102 of vehicle A being well outside the optimum viewing area D for that signal lamp. A signal indicator that generates a signal discernable in viewing area C is therefore advantageous as the driver of vehicle B can be alerted to the intent of the driver of vehicle A to change lanes, and can take appropriate action to avoid an accident in response to the viewing of the turn signal indication.
Signal mirrors generally employ one or more lamps in a mirror assembly to generate a turn indication signal. More specifically, outside signal mirrors have employed a lamp assembly positioned either behind the mirror, such that the signal light passes through the mirror, or on the rearview mirror housing, such that the signal lamp is independent of the mirror and projects light from a position either adjacent to or outside the periphery of the rearview mirror. Examples of rearview mirror assemblies incorporating turn signal indicators or other light modules positioned adjacent a rearview mirror are disclosed in U.S. Pat. Nos. 5,059,015; 5,402,103; 5,490,049; 5,497,306; 5,669,704; 5,669,705; 5,823,654; 5,863,116; 6,007,222; 6,049,271; 6,086,229; 6,119,031; 6,152,590; and 6,176,602. Rearview mirror assemblies incorporating a turn signal indicator that is directed forward of the mirror housing and subsequently directed rearward by appropriate light piping is also known in the prior art. Examples of rearview mirror assemblies where a light module is disposed behind the mirror are disclosed in U.S. Pat. Nos. D 363,920; D 394,833; D 409,540; D 425,466; D 426,506; D 426,507; D 428,372; D 428,373; D 428,842; D 429,202; D 430,088; 5,014,167; 5,207,492; 5,313,335; 5,355,284; 5,361,190; 5,436,741; 5,481,409; 5,528,422; 5,587,699; 5,619,374; 5,619,375; 5,788,537; 5,938,320; 6,005,724; 6,045,243; 6,076,948; 6,111,684; 6,142,656; 6,166,848; and 6,257,746.
FIG. 2 illustrates one example of a light module mounted behind a mirror, which happens to be an electrochromic mirror. As illustrated, rearview mirror assembly 100 includes a mirror 10, which is movably mounted within a housing 12. Housing 12 includes a mounting foot or bracket 14 for mounting the assembly to a vehicle. Mirror assembly 100 may be fixedly mounted to the outside of the vehicle or may be pivotally mounted to allow for folding of the mirror assembly. Mirror assembly 100 further includes a turn signal indicator 20 disposed behind mirror 10. The detailed construction of turn signal indicator 20 is shown in FIGS. 3 and 4 and discussed further below. As shown in FIG. 2, turn signal indicator 20 includes a plurality of light sources each disposed behind regions 22 of mirror 10 that are at least partially transmissive. These partially transmissive regions 22 may be provided in a variety of ways by either etching the reflector of mirror 10 in those regions completely or partially etching portions of the regions 22 as disclosed in commonly assigned U.S. Pat. No. 6,111,683. Alternatively, regions 22 may be formed as partially transmissive, partially reflective regions of mirror 10 or else the entire mirror 10 may include a partially transmissive, partially reflective reflector as disclosed in commonly assigned U.S. Pat. No. 6,166,848.
As shown in FIG. 3, turn signal indicator 20 may further include a sensor 56 provided to sense ambient light levels so that an associated circuit 58 may attenuate the light levels emitted by the lamps (i.e., LEDs 54). This sensor 56 may be disposed behind a region 24 (FIG. 2) that is at least partially transmissive and is similar in construction to partially transmissive regions 22 associated with the LEDs 54. As shown in FIGS. 3 and 4, LEDs 54 are mounted to a circuit board 50 that is generally parallel to the rear surface 14b of the electrochromic mirror 10. Circuit board 50 is mounted within a light module housing 52 that is secured or otherwise disposed behind the rear surface of mirror 10. As best shown in FIG. 4, LEDs 54 are typically mounted to circuit board 50 with their optical axes inclined at an angle relative to circuit board 50 so as to project light to the side and rear of the rearview mirror assembly but not back at the eyes of the driver so as to not distract the driver.
Referring back to FIG. 2, turn signal indicator 20 is electrically coupled to a turn signal actuator 26 provided in the vehicle via one or more electrical wires or cables 28. The electrochromic mirror may be connected in a variety of ways via one or more wires or cables 36 to an inside mirror control circuit 30, which in turn is coupled to an ambient light sensor 32 and a glare light sensor 34 so as to adjust the reflectivity of both the inside and outside rearview mirrors based upon ambient light levels and glare levels of light sources located to the rear of the vehicle.
An ambient light level signal may also be transmitted via a wire or cable 38 from inside mirror control circuit 30 to a variable attenuator 60 provided in the rearview mirror assembly or elsewhere in the vehicle. Variable attenuator 60 may thus be provided in addition or in lieu of sensor 56 so as to attenuate the light levels of LEDs 54 in response to ambient light sensed by a sensor remote from the outside rearview mirror housing.
The rearview mirror housing may further include a mirror position actuator (not shown), which is mounted to the inside of housing 12 and attached to the rear of mirror 10 via a carrier plate (not shown). The mirror position actuator may be electrically coupled to a mirror position controller 44 located within the vehicle via one or more electrical wires or cables 46. In this manner, the positioning of mirror 10 within housing 12 may be adjusted remotely within the cabin of the vehicle using an appropriate switch or other user input mechanism.
Additionally, rearview mirror assembly 100 may include a heater circuit provided on the rear of mirror 10 so as to heat the mirror to remove moisture such as snow, frost, or mist from the surface of mirror 10 to thereby allow clear viewing by the driver. Such a heater may be electrically coupled to a heater control circuit 40 via one or more wires or cables 42. The heater control circuit 40 may be incorporated within the vehicle climate control system such that the heater is activated whenever a window defroster/defogger is activated.
Some details of the structure shown in FIG. 4 are described further below. Additional details are disclosed in U.S. Pat. No. 6,166,848, the entire disclosure of which is incorporated herein by reference.
Of significance with respect to FIG. 4 is the fact that the LEDs 54 are mounted at an angle relative to circuit board 50. Mounting LEDs at the appropriate angle is difficult using conventional electronic component placement equipment. In general, circuit board 50 is constructed with two vias per LED 54 for receipt of two of the four LED leads. To mount the LEDs on circuit board 50, two of the leads are inserted in the two corresponding vias while the other two leads abut the same surface of circuit board 50 on which LED 54 is otherwise located. The LED leads passing through the vias are then soldered on the opposite side of circuit board 50 to make the appropriate connections and to secure LEDs 54 to circuit board 50. One problem with this approach is that two of the leads of each LED 54 are not secured firmly to circuit board 50, and the LEDs are thus prone to bending and breaking in which case performance of the turn indicator is compromised. In one prior art light module, a sealant is applied over the surface of circuit board 50, which faces the rear of the mirror. The sealant is apparently provided to protect the circuit components mounted thereon from damage due to moisture. In general, the sealant is not very effective for holding the two unsecured leads of each LED to that surface of the circuit board. Additionally, the sealant may act as a thermal insulator and not allow for sufficient dissipation of heat generated by the circuit components and the LEDs. If the heat dissipation of the LED is reduced, the amount of current that may be passed through the LED without causing failure of the LED is significantly decreased. Because the brightness of the LEDs is a direct function of the current that may be passed through the LEDs, the use of a sealant in this manner may significantly reduce the brightness of the LEDs.
Another problem associated with placing LEDs, particularly those mounted at an angle, to a circuit board behind a mirror and a rearview mirror assembly is the lack of space available for such a configuration. In direct conflict with the desire to provide a multitude of components in the outside rearview mirror body housing is a desire of vehicle designers to make the rearview mirrors as small and as aerodynamic as possible to minimize the mirror's impact of wind noise and vehicle styling. Consequently, there is not a significant volume available within the mirror housing for additional components to be placed. Further, it is desirable to make the weight of the mirror as light as possible to reduce vibration and its associated detrimental impact on rear vision. For these reasons, designers are presented with a significant challenge when attempting to design a signal mirror.
Another problem associated with placing a light module behind a mirror is properly aligning the light sources with the window regions in the mirror.
Another problem associated with providing a multitude of components such as those shown in FIG. 2 within a rearview mirror housing is the resultant difficulty in assembling the mirror housing and attaching it to the vehicle and making the necessary electrical connections. The rearview mirror assembly including an electrochromic mirror, a turn signal indicator, a heater, and a mirror position controller would typically include between three and four separate plug receptacles for connecting to associated plugs extending from the associated wiring in the vehicle. Such plugs take time to ensure proper connection with the associated receptacle, increase the number of parts, and consume additional volume within the limited space of the rearview mirror housing. Additionally, such structures typically included wires extending from the turn signal indicator, the bus bars of the electrochromic mirror, and often from the heater circuit. Such wires add to the cost of the system since they must be appropriately stripped and appropriate soldering, operations, and electrical connections must be made in addition to the fact that such operations introduce possible defects along with breaks in the wiring. In one prior art construction, a heater circuit is provided behind an electrochromic mirror. The heater circuit has three wires soldered thereto that extend to a common connector plug. Two of the three wires provide power to the heater. The third wire is coupled to a conductive trace on the heater that extends to an opposite end of the heater circuit where another wire is soldered for connection to a bus bar of the electrochromic mirror. Another wire extends from the connector plug for connection to the other bus on the electrochromic mirror. Although this construction consolidates two connector plugs into a single plug, it still utilizes four wires soldered to the heater circuit while also requiring soldering of wires to the bus bars of the electrochromic mirror.
As disclosed in commonly assigned U.S. Pat. No. 6,166,848, it is particularly advantageous to utilize what is known as a “third surface reflector” in an outside electrochromic mirror, an example of which is shown in FIG. 4. In such a third surface electrochromic mirror, two electrodes 62 and 64 are provided in electrical contact with an electrochromic medium provided within a chamber 66, which is defined between forward and rearward substrates 11 and 14, respectively, that are spaced apart with a seal 16 disposed therebetween. The forwardmost electrode 62 of the two electrodes is typically made of a transparent conductive material, while the rearwardmost electrode 64 is constructed of a reflective and electrically conductive material. The differences in material result in different resistivities of the electrodes. Accordingly, there is a preferred polarity for the electrical power to be provided to these electrodes. Specifically, it is preferable that the positive power be applied to the forward transparent electrode 62 and the ground connection be provided to the rearwardmost reflective electrode 64. Reversal of the polarity of these connections may result in damage to the electrochromic mirror. Thus, the wiring utilized to connect the electrochromic mirror to the appropriate mirror control circuit could readily be connected in the wrong positions within a plug receptacle thereby accidentally causing damage to the electrochromic mirror. Thus, the use of a third surface electrochromic mirror may further add to the difficulties in providing proper electrical connections to all the components disposed within a rearview mirror housing.